This invention relates generally to the field of dental implants and their use, more particularly to the preparation of crestal bone surrounding an implant at the site of installation for receiving a dental restoration on the implant.
U.S. Pat. No. 5,338,196 (which is owned by the Assignee of the present application) teaches, among other things, a second-stage healing abutment for forming and preserving in the mucosa above a dental implant a transmucosal opening large enough to receive an artificial tooth which faithfully replicates a natural tooth being restored. This opening expands in size from the implant to the outer surface of the overlying gingiva, where the opening has width approximating that of the lost natural tooth being replaced, where it emerged from the gums. During the first stage of dental implantation, however, when the implant with its cover screw is left unloaded in the jawbone for a time interval while osseointegration proceeds, the crestal cortical bone tends to grow over the periphery of the cover screw, and this overgrowth must be removed at the beginning of the second stage, if only to permit the cover screw to be removed from the implant. Removing this bone overgrowth is now done by hand. This practice is tedious and imprecise, and potentially harmful to the patient.
According to the present invention an expanding hole is formed in the crestal bone surrounding the gingival surface of the implant, the shape of which hole preferably matches and mates with the expanding hole in the overlying gingiva. In this preferred embodiment of the invention there is presented to the restoring dentist a continuous tapered hole from the gingival surface through the gingiva and the underlying crestal bone to the surface of the implant, through which to instal an artificial tooth on the implant. The present invention further provides improved means for forming a desired hole in the crestal bone accurately and precisely shaped and positioned with relation to the implant, and without damaging the bone or the implant surface. More particularly, the present invention teaches a new bone mill using teeth with a negative rake to provide a passive cutting action which minimizes damage to the bone and to the surface of the implant, together with a method of using it which emphasizes low speed turning. The present invention provide means to limit the progress of the bone mill toward the implant surface, which further safeguards the surface of the implant.
The present invention improves and enhances the utility of the second-stage healing abutment which is taught in the ""196 patent, which is now provided with improved access to the implant and can be seated with assured precision on the implant. Since the process of making an artificial tooth begins with the healing abutment, these benefits flow through to the artificial tooth that will ultimately be installed on the implant.